Electrical actuators including motors and solenoids are used in numerous applications to provide controlled translation of mechanical components. All such actuators comprise, in one form or another, at least one electrical coil characterized by inductive and resistive electrical parameters. Mechanical response time of an actuator to energization of the coil, hereafter pull-in response, is often limited by the time required to develop current in the coil since the force acting on the actuator is proportional to the current. Generally, high force generating coils--that is to say solenoid structures characterized by relatively numerous coil turns--have slower current rise times due to the proportional correspondence between coil turns and inductance.
As a practical matter, all systems have a limitation on the source voltage which comprises the forcing function for the current development in accord with natural and forced response characteristics of the energized circuit. For example, in conventional automotive applications, the source voltage and hence the forcing function is substantially 12 volts. The inductive and resistive electrical parameters of the electrical coil together with the source voltage parameter therefore limit the response of the actuator.
Another characteristic of electrical actuators of the inductive variety presents certain challenges for mechanical response of the actuator upon deenergization of the coil. The energy stored in the coil due to the current flowing therethrough while energized requires management to prevent overvoltage damage to solid state drive circuitry and to ensure adequately swift dissipation in applications where minimization of mechanical response time of the actuator to deenergization of the coil, hereafter drop-out response, is an objective of the system. Known techniques for inductive current management include use of anti-parallel diode arrangements for dissipating the inductive energy. Generally, however, faster actuator drop-out response is achieved with faster energy dissipation which, of course, requires robust snubber diode arrangement.
As can be seen, performance shortfalls exist at both ends of an energization cycle for electrical actuators of the inductive variety.